CodeEval - Distinct Subsequences - Hard

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;


public class Main {

    public static void main(String[] args) throws FileNotFoundException, IOException {

        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        StringBuffer sb = new StringBuffer();
        String line;
        while ((line = in.readLine()) != null) {
           StringTokenizer st=new StringTokenizer(line,",");
           wholeStr=st.nextToken();
           str=st.nextToken();
           sb.append(getOccurence(0, 0, new StringBuilder()));
           sb.append('\n');
        }
        System.out.print(sb);
    }
   
    static String str;
    static String wholeStr;
   
    static int getOccurence(int j,int i,StringBuilder string){
        if(j==str.length())
            return 1;
        if(i==wholeStr.length())
            return 0;
        int counter=0;
        if(str.charAt(j)==wholeStr.charAt(i)){
            counter=getOccurence(j+1,i+1,string);
        }
        return  getOccurence(j,i+1,string)+counter;
    }

}